During the firing of greenbodies to form sintered casted products, the greenbodies can undergo substantial shrinkage and deformation. For example, the casting of some medical components, such as a jaw of a device having forceps by metal injection molding (herein “MIM”), results in the intermediate formation of a molded greenbody that is subsequently fired to create the final product. During the heating and densification, the greenbody has a tendency to shrink. Such shrinkage can lead to an undesirable deformation of a greenbody. For example, when the greenbody has a section with a relatively more massive, larger cross section connected to a section with a relatively less massive, smaller cross section, the differential shrinkage between the sections can lead to differential stress formation between the sections that anisotropically distorts the shape of the fired product. In another example, sections of a greenbody that are extensions supported by a connection to a body can become misshapen during firing due to gravitational forces acting on the extension.
These potential misshapened products can result in the need for secondary straightening operations to correct variations in camber and/or tailwag effects after sintering. Beyond being time consuming, such operations also increase the cost of producing casted pieces. Furthermore, in some situations, secondary operations may not be able to adequately correct shape defects. In such cases, there is a decrease in product yield, which is directly related to loss of properly formed product.
Accordingly, a need exists for improved methods and devices that increase the quality of molded pieces, and in particular, decrease the probability of forming misshapened products during greenbody densification.